Navigation, power and communications systems that rely on GPS satellite navigation will be disrupted by violent solar activity in 2011, research shows.

A study reveals Global Positioning System receivers to be unexpectedly vulnerable to bursts of radio noise produced by solar flares, created by explosions in the Sun's atmosphere.

When solar activity peaks in 2011 and 2012, it could cause widespread disruption to aircraft navigation and emergency location systems that rely heavily on satellite navigation data.

Particularly intense solar activity occurs roughly every 11 years due to cyclic changes to the Sun's magnetic field – a peak period known as the solar maximum.

Solar flares send charged particles crashing into the outer fringes of the Earth's atmosphere at high velocity, generating auroras and geomagnetic storms.

Radio noise
Charged particles from solar flares also produce intense bursts of radio noise, which peak in the 1.2 and 1.6 gigahertz bands used by GPS. Normally, radio noise in these bands is very low, so receivers can easily pick up weak signals from orbiting satellites.

In 2005, however, Cornell University graduate student Alessandro Cerruti discovered a puzzling failure in GPS reception while operating a receiver at Arecibo Observatory in Puerto Rico.

Along with Paul Kintner, from the university's electrical engineering department, Cerruti traced the problem to a radio burst induced by a solar flare. They found that GPS receivers operated by the US Federal Aviation Administration (FAA) and the Brazilian Air Force experienced similar disruption during this burst of solar activity.

The researchers say the problem has escaped detection before because GPS systems have spread in popularity during a time of relatively low solar activity.

Drowned out
Discovering the disruption was surprising. "[Other] people will be surprised at the next solar maximum," Kintner says. Both the number and intensity of radio flares will increase and could drown out GPS signals during this period, he says.

This may be a problem for aircraft navigation. The FAA uses GPS receivers for air traffic control, which Kintner says "will certainly fail" during these intense solar flare radio bursts, which could cause signals to drop by up to 90%, for hours at a time. Although planes can fly without GPS, outages force the FAA to increase the distance between aircraft and slow take-offs and landings, delaying flights.

GPS is also used for emergency rescues and also to synchronise power grids and cellphone networks. One solution, says Kintner, would be to increase the strength of GPS signals. But this would mean redesigning GPS satellite hardware and software

Cerruti presented details of the problem at a meeting of the Institute of Navigation on 28 September. Details will be published in a forthcoming issue of the journal Space Weather.